The owners of household pets, particularly cats, perceive the development of odors in animal litter boxes as a significant problem. Attempts to alleviate this problem have ranged from the addition of perfume and odor adsorbents to mask or adsorb odors once formed, to the use of chemical or physical treatments of the litter to prevent odor formation. These approaches have met with limited success due to several factors: lack of acceptance by the animal resulting in avoidance of the litter box; expense of the treatment; inconvenience of practical use; and/or concerns of safe exposure of the chemical agents employed to the animal and/or pet owner.
Prior art attempts to deal with odors following their formation include the use of cyclodextrin in animal litter as both a nitrogenous compound absorber and as a fragrance carrier, as disclosed in U.S. Pat. No. 4,844,010 issued on July 4, 1989 to Ducharme et al. Unfortunately, household pets often dislike the smell of such products and avoid the use of the litter. Moreover, since these materials must mask odors, they are effective only over a limited period of time.
Animal litter odors have also been dealt with by the use of deodorizers. U.S. Pat. No. 4,203,388 issued on May 10, 1980 to Cortigene et al. teaches the use of a deodorant, such as sodium bicarbonate, in amounts of between about 1% and about 10% of the dry weight of the litter. Such large amounts of deodorizer are necessitated since the litter itself is also used as an absorbent for urine, requiring the deodorizer to be homogeneously dispersed throughout the particles of the litter.
U.S. Pat No. 3,965,863 issued on June 29, 1976 to Scott describes a chemical litter unit with separate holding tanks for solid and liquid excreta, with appropriate chemical solutions for deodorizing purposes in each tank. Non-absorbent chips are suggested as a re-usable litter. This system requires intimate contact of the pet owner with both excreta and with the chemical solutions used as deodorizers. The device is expensive to manufacture, as well as expensive and inconvenient to maintain.
U.S. Pat. No. 4,534,315 issued on Aug. 13, 1985 to Sweeney discloses an animal litter container employing an upper layer of material which is substantially non-absorbent to moisture, such as sand, over a layer of moisture-absorbent material such as clay, separated by a foraminous liquid-permeable barrier intended to reduce odors emanating from the lower layer. However, no means are provided to prevent the formation of such odors. Furthermore, the foraminous barrier must strike a balance between ease of fluid passage to the absorbent layer on the one hand versus the escape of odors from the lowermost absorbent layer on the other, e.g. larger and more numerous perforations in the barrier layer will allow more rapid and complete passage of fluid to the absorbent layer, but will also provide a means for odors to more readily escape from the lowermost absorbent layer.
The prior art also discloses attempts to prevent the formation of certain unpleasant odors. For example, U.S. Pat. No. 4,405,354 issued on Sept. 20, 1983 to Thomas et al. discloses the use of buffering agents to prevent gaseous ammonia from escaping into the air. However, such buffering agents serve only to prevent the formation of gaseous ammonia, doing nothing against other unpleasant odors. Further, the amounts of such agents range from about 0.5% to about 25% by weight, since all of the absorbent litter must be treated with the agent to provide sufficient contact with the urine.
Fungicides and bacteriostats have also been disclosed in the prior art as means to prevent the formation of odors in animal litters. U.S. Pat. No. 4,517,919 issued on May 21, 1985 to Benjamin et al. discloses the use of undecylenic acid in amounts from about 1000 to about 10,000 ppm and a bacteriostat in amounts from about 25 to 500 ppm. High concentrations of these materials are necessary, since any portion of the absorbent litter may be exposed to urine.
Still other prior art methods for preventing odor development from bacterial action have included heating to destroy bacteria, and desiccation of the litter by heat or evaporation. U.S. Pat. No. 4,649,862 issued on Mar. 17, 1987 to Neary discloses a sanitizing device for the litter box which applies heat to the litter to destroy bacteria. However, this device hastens the evaporation of urine into the air, thereby increasing the severity of the odor associated with the urine.
All of the aforementioned prior art references disclose odor abatement means intended to function in the animal litter itself. Another known prior art odor abatement system employs a litter box liner which acts in conjunction with the litter. U.S. Pat. No. 4,852,518 issued on Aug. 1, 1989 to Yananton teaches the use of a sorbtive-desiccant pad structure to prevent significant odor formation. The patent teaches that the pad disperses and evaporates the urine, causing bacteria to die or become dormant, and thereby preventing odor formation. Non-absorbent litter is employed to aid liquid transfer to the pad. However, as pointed out earlier herein, rapidly evaporating urine into the air may lead to significant odor due to the inherent odor of the animal urine itself, regardless of the absence of bacterial action. Furthermore, Yananton teaches the use of only one quarter to one half inch of granular litter in order to allow the evaporation of urine to occur. Normally, at least two to three inches of granular litter are required to afford the animal an opportunity to bury its solid waste. The use of such small amounts of litter tends to discourage the animal from using the litter box. In addition, it can result in significant odors emanating from unburied fecal matter.
U.S. Pat. No. 4,494,482 issued on Jan. 22, 1985 to Arnold also discloses the use of an absorbent pad to prevent odor formation. This patent further teaches the use of about 5,000 to about 30,000 ppm of a bacteriostat in the absorbent pad to control odor. Because these pads are used in conjunction with absorbent litter, e.g.. clay, the suggested amounts of bacteriostat in the pad are extremely high to account for the large amount of untreated litter in the litter box. According to the patent's teachings, a pad weighing 50 grams used in conjunction with 2,000 grams of untreated clay must contain 4,100 ppm of bacteriostat in order to maintain an overall level of 100 ppm of bacteriostat in the combined material in the litter box. Such high levels of bacteriostat are generally undesirable from the standpoint of safe levels of exposure to the pet and the pet owner, as well as from the standpoint of materials cost.
Accordingly, it is a principal object of the present invention to provide an animal excrement collection system which prevents the development of unpleasant odors over an extended period of time, which minimizes the amount of odor abating agents which must be used for reasons of safety and expense, which minimizes contact of the pet and pet owner to excreta and odor abating agents and which is accepted for use by the pet.
It is a further object of the present invention to provide such an animal excrement collection system which is inexpensive and which is widely adaptable to fit a variety of commercial litter boxes currently marketed.
A further object of the present invention is to provide a method of preparing the litter box system.